zooplankton spatial distribution and community …
TRANSCRIPT
Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 4, No. 2, Hlm. 247-258, Desember 2012
©Ikatan Sarjana Oseanologi Indonesia dan
Departemen Ilmu dan Teknologi Kelautan, FPIK-IPB 247
ZOOPLANKTON SPATIAL DISTRIBUTION
AND COMMUNITY STRUCTURE IN BANGGAI SEA
Arief Rachman and Elly Asniariati
Research Center for Oceanography, Indonesian Institute of Sciences
Jl. Pasir Putih I, Ancol Timur, Jakarta Utara. Email: [email protected]
ABSTRACT
Banggai Sea is an interesting ecosystem due to mixing influences from Banda Sea in
the west and Maluccas Sea in the east. Therefore, a unique zooplankton community
structure and specific distribution pattern should be found in this area. This research was
carried on using Baruna Jaya VIII research vessel and samples were collected in 14
sampling stations. Vertical towing using NORPAC plankton net (300 µm) was
conducted to collect zooplankton samples. Result showed that inner Mesamat Bay had
the lowest abundance of zooplankton, probably due to low water quality resulted from
anthropogenic activity. Meanwhile the strait between Liang and Labobo Island had the
highest zooplankton abundance in Banggai Sea. Calanoids was the dominant
zooplankton taxa in the ecosystem and contributing 55.7% of total density of
zooplankton community. The highest importance value made this taxa to be very
important factor that regulates the lower trophic level organisms. Results also showed
that zooplankton was distributed nearly uniform in eastern but aggregated to several
stations in western Banggai Sea. Zooplankton abundance was higher in the central of
Banggai Sea, compared to western and eastern area. According to Bray-Curtis
clustering analysis the strait between Liang and Labobo Island has unique zooplankton
community structure. This might happened due to mixing of water from two highly
productive seas that influenced the Banggai Sea ecosystem. From this research we
conclude that this strait probably was the zooplankton hot spot area which might also
indicate that this area also a hot spot of fishes in the Banggai Sea.
Keywords: spatial distribution, zooplankton, community structure, hot spot, Banggai
Sea.
I. INTRODUCTIONS
One characteristic of planktonic
population, including zooplankton
population, is that they tend to form
patches that vary on a scale of few meters
to hundreds of kilometers (Nybakken and
Bertness, 2005). This patch occurs due to
influence of many physical and chemical
parameters in the water. The most
common water parameters that regulating
this patchiness in marine ecosystems are
dissolved oxygen, temperature, salinity,
turbidity, pH and water movement (Horne
and Goldman, 1994; Nybakken and
Bertness, 2005; Hsiao et al., 2011). Thus
large-scale patchiness that occur in marine
ecosystem might happened due to changes
in the stability of water column, resulting
in changes in nutrient availability for
plankton in the ecosystem (Nybakken and
Bertness, 2005; Escribano et al., 2005).
Most of zooplankton organisms are
sensitive to fluctuation in water
parameters, thus it inducing changes in
abundance and also regulate the
distribution of various zooplankton
genuses in the ecosystems (Hsiao et al.,
2011). Zooplankton also tends to form
clump or patch of high density population
at areas with high phytoplankton
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248 http://itk.fpik.ipb.ac.id/ej_itkt42
abundance (Nybakken and Bertness,
2005).
Banggai Sea is heavily influenced
by Banda Sea and Moluccas Sea, two
productive seas in Indonesia due to
seasonal upwelling event (Asriyana dan
Yuliana, 2012). Both Banda Sea and
Moluccas Sea were part of Indonesian
Throughflow (ITF) system which
connecting the water masses between
Pacific Ocean and Indian Ocean (Gordon
and Susanto, 2001; Sprintall et al., 2009).
Mix of waters from those seas not only
resulting in high diversity of marine
organisms in Banggai Island, it also
sustain various types of ecosystems such
as mangrove forests, marine dominated
estuaries, coral reefs and seagrass bed.
Monsoon system that heavily affected the
condition of Banda Sea and Moluccas Sea
(Baars et al., 1990; Gordon and Susanto,
2001), might also affecting the condition
of water parameters in Banggai Sea. The
mix of water masses from Banda Sea and
Moluccas Sea should affect the
zooplankton community structure and
spatial distribution in Banggai Sea. It was
hypothesized that the mixing area in
Banggai Sea should become the center of
zooplankton abundance and probably has
different community structure compared
to Banda Sea and Moluccas Sea. The aims
of this research are to understand the
community structure and spatial
distribution pattern of zooplankton in
Banggai Sea related to with the
phytoplankton community in the
ecosystem.
II. METHODS
2.1. Study Sites
Banggai Sea was a part of Banggai
Island archipelago which located eastern
from South Celebes (Figure 1). This area
was known for its high diversity in marine
organism and marine ecosystems, such as
marine dominated estuaries, mangrove
forests, coral reefs, seagrass beds and
coral reefs. Oceanic atolls and wide reef
flat was found in Karang Merpati and
known as hotspot for fish diversity in
Banggai Sea. The water of Banggai Sea
was a mix of water masses from two
highly productive seas, the Banda Sea and
Moluccas Sea. This condition created a
high productive water thus creating
several area which known as hot spot for
fisheries in Banggai Sea. There are 7
islands that surrounding Banggai Sea,
which were Liang, Tinangkung, Banggai,
Lo Bangkurung, Labobo, Melilis and
Timpaus (Figure 1).
2.2. Field Sampling
This research was conducted using
Baruna Jaya VIII, a research vessel
belongs to Research Center for
Oceanography, Indonesian Institute of
Sciences during Banggai Island
Expedition in 16 June – 8 July 2011.
Plankton sample was taken in 14 sampling
stations around Banggai Sea (Figure 1)
during night time. Zooplankton sampling
was done with vertical towing method
using NORPAC plankton net (mouth 0.45
m; length 1.8 m; mesh 300 µm).
Flowmeter was attached in the mouth of
plankton net to measure volume of filtered
water, using formula as described by
Arinardi in Hutagalung et al. (1997).
In this research most sampling was
done from depth of 200 m, although in
some shallow areas sample was collected
from depth of 20, 60, 70, 80 or 150 m.
After each towing, plankton net was
soaked with seawater to release some
zooplankton that trapped in the net.
Filtered zooplankton sample was collected
in 250 ml polyethylene bottle and fixated
with 4% formaldehyde.
Rachman dan Asniariati
Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 4, No. 2, Desember 2012 249
Figure 1. Map of Banggai Sea and the location of sampling stations in this research. The
sampling stations divided into western, middle and eastern zone of Banggai
Sea.
2.3. Zooplankton Identification and
Enumeration
Zooplankton identification and
enumeration was done in Plankton and
Primary Productivity Laboratory,
Research Center for Oceanography,
Indonesian Institute of Sciences.
Identification and enumeration of
zooplankton individuals was done by
conducting fraction method, taken with
2.5 ml stample pipette. Fractioned sample
was then placed in Bogorov counting tray
and observed using LEICA MZ-6 stereo
microscope under 4 – 40 X magnification.
Identification was done up to genus level
using references from Shirota (1966),
Yamaji (1966), Nontji (2000), Wickstead
(1976). Estimation of zooplankton
individual in the sample was done by
using formula as described by Semina in
Sournia (1978).
2.4. Data Analysis
The data was analysis by generating
biotic parameters, such as absolute
density, relative density, absolute
frequency, relative frequency and
importance value of all zooplankton taxa
in Banggai Sea (Cox, 1976). The data was
also analyzed with Shannon-Wienner
indices of diversity, simple regression and
correlation. A contour map representing
pattern of zooplankton abundance was
created using Surfer ver. 8.0 Surface
Mapping System, to understand the spatial
distribution pattern of zooplankton in
Banggai Sea. Bray-Curtis Cluster
Analysis (Simple Average Link) was
conducted using BioDiversity
Provessional Ver. 2 to understand the
trend of different zooplankton community
structure in the sampling stations
(McAleece et al., 1997).
III. RESULTS AND DISCUSSIONS
3.1. Zooplankton Community Structure
in Banggai Sea Ecosystem
From this research it was found that
calanoids was the dominant taxa in the
zooplankton community of Banggai Sea.
The density of calanoids found in the
Lo Bangkurung
Bulagi
Tinangkung
Banggai
Labobo
Melilis
Timpaus
Liang Mesamat Bay
Peleng Bay
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250 http://itk.fpik.ipb.ac.id/ej_itkt42
water column of Banggai Sea was 6,119
ind.m-3
and contributing 55.70% to total
number of zooplankton in the community
(Fig 2A and 2B). Calanoids was found
widely distributed in the Banggai Sea and
could be found in all sampling stations in
this research (Figure 2C).
Based on importance value analysis,
calanoids has the highest importance
value, thus making this taxa have a
significant role in the zooplankton
community of Banggai Sea (Figure 2D).
High abundance of calanoids in the water
column was common in tropical oceanic
ecosystem, such as in Southwestern
Atlantic and West Africa (Neumann-
Leitao et al., 2008; Champalbert et al.,
2005).
Aside from calanoids, cyclopoids
was found have the second highest density
(Figure 2A and 2B) and have importance
value of 15.19% (Figure 2D). These taxa
were also widely distributed in Banggai
Sea and could be found in all sampling
stations (Figure 2C). This pattern of
widely distributed copepods, indicating
that circum-global distribution pattern was
more common than endemism in Banggai
Sea. This might also related to the lack of
freshwater runoff from the islands around
the study area, because of the season or
the basic geomorphology of the area
(Neumann-Leitao et al., 2008). The other
zooplankton taxa that have high
abundance in this research were
oikopleurans, ostracods and chaetognathes
(Figure 2A and 2B). These three taxa were
also have relatively high importance value
in the community compared to other
zooplankton taxa in this research (Figure
2D). The importance value of
oikopleurans, ostracods and
chaetoghanthes were 14.25%, 11.75% and
9.35% respectively. Relatively high
abundance of ostracods in this research
was characteristic for oceanic
environment in oceans (Riandey et al.,
2005).
From this research it also found that
the abundance of macro-crustaceans, such
as mysids and brachiopods, were very low
compared to other zooplankton taxa
(Figure 2A and 2B). Both taxa were only
found in one station in this research, thus
making mysids and brachiopods have
quite low frequency (Figure 2C). This
result indicating that the distribution of
brachiopods and mysids in Banggai Sea
were very limited to some stations, which
have the most suitable water parameter for
those two taxa. It assumed that
brachiopods and mysids found in this
research has narrow tolerance range, thus
changes in water parameters would limit
their spatial distribution.
3.2. Zooplankton Spatial Distribution in
Banggai Sea
A distinct pattern of different
zooplankton density was found in
sampling station belong to three zones of
Banggai Sea (Figure 3). In general, the
middle zone of Banggai Sea holds the
highest mean zoooplankton abundance
compared to two other zones (Figure 3B).
Figure 3A showed that station 9, which is
a strait between Labobo and Liang (Figure
1), has the highest zooplankton
abundance, with density of 1,722 ind.m-3
.
Meanwhile station 8 that located in the
inner Mesamat Bay, has the lowest
zooplankton abundance (Fig 3A), despite
of it location which inside a large bay and
near the coast of the largest island in
Banggai Sea (Figure 1). The density of
zooplankton individuals in station 8 was
only 339 ind.m-3
(Figure 3A). This station
should have high abundance of
zooplankton due to high influence of land
run-off or local topographic upwelling
which enriches the water column
(Neumann-Leitao et al., 2008).
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Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 4, No. 2, Desember 2012 251
Figure 2. Zooplankton community structure of Banggai Sea ecosystem. (A) absolute
density; (B) relative density; (C) frequency; and (D) importance value.
(A) (B)
(C) (D)
Individuals/m3
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Figure 3. Zooplankton abundance in the sampling stations around Banggai Sea. (A)
zooplankton absolute density in each sampling station; (B) average
zooplankton density in three zones of Banggai Sea
The contour map of zooplankton
abundance in Banggai Sea clearly showed
that zooplankton abundance was centered
on station 9 (Figure 4). This area could be
designated as the hot spot zone for
zooplankton distribution in Banggai Sea
(Figure 4). This result also showed
different trend of zooplankton patchiness
in three zones of Banggai Sea. It was clear
that stations in the middle zone of
Banggai Sea have higher abundance of
zooplankton compared to stations in the
eastern and western zone (Figure 4).
The zooplankton population showed
high patchiness in the middle area, with
center of distribution located at station 9,
12 and 11 (Figure 4). Meanwhile the
eastern zone, which heavily influenced by
water mass from Moluccas Sea, seems to
have homogenous zooplankton spatial
distribution (Figure 4). This trend
indicating that the water condition of
eastern zone of Banggai Sea probably
much more homogenous compared to two
other zones, especially the middle zone.
The relatively homogenous condition of
water column in this research is a
common characteristic of oceanic
environment or region (Rakesh et al.,
2006).
Further analysis on distribution
pattern of zooplankton diversity in the
Banggai Sea showed different patchiness
pattern (Figure 5). Station 9 which has the
highest abundance of zooplankton (Figure
4) was not the area with the highest value
in Shannon-Wienner diversity indices
(Figure 5). From Figure 5 it was clear that
station 10 was the area with the most
diverse zooplankton taxa in the Banggai
Sea, with the value of 1.89. Based on this
result, it was clear that station 8 is the area
with the lowest diversity of zooplankton
in Banggai Sea, with the value of 1.27
(Figure 5). This similar pattern also
observed in the contour map of
zooplankton abundance in the waters of
Banggai Sea (Figure 4).
(A) (B)
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Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 4, No. 2, Desember 2012 253
Figure 4. Contour map of zooplankton abundance in Banggai Sea, which also give clues
to the trends in zooplankton spatial distribution and patchiness.
Figure 5. Contour map of zooplankton Shannon-Wienner indices of diversity. Different
trend of zooplankton patchiness was observed from the result of this analysis.
3.3. Grouping of Sampling Stations
Based on Zooplankton
Community Structure
Bray-Curtis cluster analysis
suggested four groups that were
different from the each other’s (Figure
6). It suggested that there were at least
four unique zooplankton community
structures in the Banggai Sea
ecosystem. The similarity of community
structure in each group was probably
occurred due to similar condition of
water parameters in the stations inside
the group.
Zooplankton Spatial Distribution and Community Structure…
254 http://itk.fpik.ipb.ac.id/ej_itkt42
Figure 6. Dendogram resulted from Bray-Curtis cluster analysis of zooplankton
community structure in each sampling station. Station 2, 3, 5, 6, 7 located in
eastern area; Station 8, 9, 10, 11, 12 located in middle area; Station 13, 14,
15, 16 located in western area.
Surprisingly the community
structure of the sampling stations in this
research showed no significant differences
between three zones in Banggai Sea
(Figure 6). It was assumed that
zooplankton abundance and community
structure in the middle zone’s sampling
stations were different from eastern and
western zone. But in this result, it was
clear that group 3 consist of stations that
located at three different zones in this
research (Figure 6). In group 3 (Figure 6),
station 15, 14 and 12 located at western
zone, meanwhile station 3, 5 and 6 located
at eastern zone of Banggai Sea (Figure 3
and 4). In general, this trend indicating
that there were no significant differences
in zooplankton community structure
among the western, middle and eastern
area of Banggai Sea. Although the results
also showed that the spatial distribution
(Figure 4) and the abundance (Figure 3) of
zooplankton was different in those areas.
3.4. Zooplankton Patchiness in Banggai
Sea
High patchiness of zooplankton
population (Figure 4), high diversity
(Figure 5) and high variation of
zooplankton abundance (Figure 3A) in the
middle zone of Banggai Sea, indicate that
the water condition was heterogeneous.
On the other hand, the most suitable
condition for high population growth of
zooplankton was only available in limited
areas, such as station 9, 11 and 12. This
condition might be happened due to
mixing of different water masses from
Moluccas Sea and Banda Sea which
influence the Banggai Sea ecosystem.
Highly aggregated zooplankton
patchiness in the water could occur due to
mixing and upwelling event in the water
column (Escribano et al., 2005). The
water from those two productive seas
might carry nutrients that mixed together
in the middle zone of Banggai Sea, thus
enriching the water and increase the
(1)
(2)
(3)
(4)
70
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Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 4, No. 2, Desember 2012 255
primary production. In the end this
condition was favorable for zooplankton
and supporting the growth of its
population. Station 9, which become the
hot spot for zooplankton abundance in this
research, was located in the strait between
two islands (Figure 1 and 4) and probably
also located in the mixing zone.
The present of coastal front or shelf
break in station 9 might created vertical
turbulence or upwelling events when two
water masses from Moluccas and Banda
Sea meets. This will enrich the water
column with nutrients that support high
phytoplankton growth, and then support
high zooplankton growth in the water
column (Nybakken and Bertness, 2005;
Neuman-Leitao et al., 2008; Champalbert
et al., 2005). Another indication of
relatively high upwelling events in
Banggai Sea was the frequent occurrence
of harpacticoids, the commonly benthic
copepods. In this research harpacticoids
could be found at 12 sampling stations,
except at station 2 and 14.
Aside from the effect of physical
factor, it assumed that the pattern of
zooplankton patchiness in Banggai Sea
was related to distribution of
phytoplankton in the waters. When the
data of zooplankton abundance in each
station was combined with phytoplankton
abundance, it was noted that at some
point, there are similarity in the trend
(Figure 7).
Although inconsistency was found
in the term of station with the highest
abundance in phytoplankton and
zooplankton, the station with the lowest
abundance remains the same, which is the
station 8 (Figure 7). Very low abundance
of phytoplankton might be the main
reason for the low abundance of
zooplankton in station 8. Unfortunately it
is unknown why the high abundance of
zooplankton in station 9 seems unrelated
with the abundance of phytoplankton in
adjacent station (Figure 7). Simple
correlation analysis showed low positive
relationship between zooplankton and
phytoplankton in Banggai Sea, but this
correlation was statistically insignificant (r
= 0.1292; p >0.05). The simple linear
regression showed a trend that an increase
in phytoplankton abundance should be
followed by an increase in zooplankton
abundance (Figure 8).
Figure 7. Combined histogram of zooplankton abundance and phytoplankton abundance
in the Banggai Sea.
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Figure 8. Regression graphic of zooplankton and phytoplankton in Banggai Sea waters.
a positive trend was observed, although with very low R2 value
The result of correlation and
regression analysis (Figure 8) showed that
phytoplankton community was not strong
enough to act as main regulating factor for
zooplankton patchiness in the Banggai
Sea. But the positive correlation and
regression trend (Figure 8) clearly showed
an interaction between zooplankton and
phytoplankton community, which should
observed in the form of predator-prey
relationship.
3.5. Zooplankton Hotspot as Center for
Marine Fishes Distribution in
Banggai Sea
It was not surprising that station 9,
the hot spot of zooplankton abundance,
has a unique community structure which
very different from the others (Figure 5).
This distinctive community structure
probably occurred due to the mix of
different water masses and the present of
coastal front in station 9. This condition
might be favorable for the growth of
zooplankton and in the end it might also
favorable for the growth of
zooplanktivorous fishes in Banggai Sea.
As widely known, zooplankton was very
important component in marine food web
that support the growth of fish community
in the ecosystem (Nybakken and Bertness,
2005; Hsiao et al., 2011; Escribano et al.,
2007). Thus one determining factors of
commercial fisheries production in marine
ecosystem was the production of pelagic
zooplankton, the population fluctuations,
and the community structure of
zooplankton (Bednarski and Morales-
Ramirez, 2004). In some tropical areas,
such as tropical Atlantic Ocean at West
Africa, zooplankton was regarded as
important food for tuna preys, thus it also
regulating the abundance of tuna in the
ocean (Champalbert et al., 2005). Based
on result of this research, it was assumed
that the hot spot area of zooplankton
distribution might also become the hot
spot area of fishes in Banggai Sea.
IV. CONCLUSSION
From this research it can be
concluded that patchiness in zooplankton
spatial distribution was assumed related to
the mixing of water masses from
Moluccas Sea and Banda Sea. High
abundance and unique zooplankton
community structure in the strait between
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Jurnal Ilmu dan Teknologi Kelautan Tropis, Vol. 4, No. 2, Desember 2012 257
Liang and Labobo Island indicated that
this area might be a hot spot of
zooplankton in Banggai Sea.
ACKNOWLEDGEMENTS
This research was conducted during
Banggai Sea Expedition, part of Transfer
Knowledge program in 2012, which
funded and supported by Research Center
for Oceanography, Indonesian Institute of
Sciences. We would like to give our great
appreciation to all crew of Baruna Jaya
VIII research vessel which facilitates this
research and greatly assist us in sample
collection during the expedition. We also
express our great appreciation to Ms.
Hikmah Thoha, M.Sc., which helped us in
sample collecting. We also give our
sincere gratitude to Ms. Nurul Fitriya,
M.Sc., for the very helpful discussion on
our research theme.
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